Imaginable (adjective)

1. Capable of being imagined; conceivable.
2. Able to be formed in the mind as a mental image.
3. Possible to conceive or imagine.

Origin:

From the verb imagine, from latin imaginari, to form an image of, from imago, image.

Examples:

1. The idea of traveling to space was once unimaginable, but now it is a reality.
2. The amount of money he won was unimaginable to most people.
3. The horrors of war are unimaginable for those who have never experienced it.
4. The progress in technology in the last century is almost unimaginable.
5. The devastation caused by the natural disaster was unimaginable.